How do I automatically implement protocols/extensions/conformance in Swift?

[boehs]

I have many structs and enums that need to be Codable, among others. Right now, what I do is I have mirror types named FFI* and funcs for conversion:

// shared.swift

// Note that we don't yet support `indirect` for enums.
// See https://github.com/mozilla/uniffi-rs/issues/396 for further discussion.
public enum FfiReviewUpvoteStatus {
    case upvote
    case neutral
    case downvote
}

// otherCode.swift

enum ReviewUpvoteStatus: Hashable, Codable {
    case upvote, downvote, neutral
    
    init(ffi: FfiReviewUpvoteStatus) {
        self = switch ffi {
            case .upvote:
                Self.upvote
            case .downvote:
                Self.downvote
            case .neutral:
                Self.neutral
        }
    }
}

Automatic synthesis got you covered when they are there on initialization, but if you somewhere else write an extension to conform

// otherCode.swift
extension FfiReviewUpvoteStatus: Codable {} // Extension outside of file declaring enum 'FfiReviewUpvoteStatus' prevents automatic synthesis of 'encode(to:)' for protocol 'Encodable'

It doesn't go so well. Implementing these manually inside an extension is forbidingly difficult. One potential thing I considered is just finding and replacing the output swift but come on ;) Maybe some sort of macro like

#[derive(Debug, uniffi::Enum)]
#[uniffi::implements(swift("Codable"))]
pub enum FFIReviewUpvoteStatus {
    Upvote,
    Neutral,
    Downvote,
}

akin to serde?

Edit: it might also just be possible to add Codable to everything. Worth looking into if that incurs an expense.